This invention relates to disc brakes the so-called floating caliper type.
Conventional floating caliper type disc brakes comprise a pair of friction pads disposed on opposite sides of a rotatable disc, a caliper straddling a portion of the circumference of the disc, an actuator such as a hydraulic cylinder piston device incorporated in the caliper and on one side of the disc for pressing one of the friction pad against the disc and displacing the caliper so that the other friction pad is pressed against the disc, and a stationary holder secured to a non-rotatable part of a vehicle and mounting the caliper thereon so as to move in the direction towards and away from the disc. The friction pads are usually supported by a pair of pins which are secured to the caliper, or otherwise, the friction pads are slidably supported on shoulders formed on the holder. However, there are problems in that vibrations of the friction pads have been experienced during running of the vehicle, thereby generating noisy sounds and injuring or wearing the friction pads and supporting portions.
For solving the problems aforementioned, there has been proposed a disc brake having a pad spring interposed between the caliper and the friction pads for pressing the friction pads generally in the direction radially inwards with respect to the disc. However, when the wear of the friction pads increases, the piston of the cylinder piston device projects out of the cylinder to compensate for the wear so that the friction pad on the side of the piston is displaced in the direction away from the cylinder, or in the direction approaching the other friction pad. When the friction pad on the side of the piston is displaced toward the other friction pad, the force of the pad spring acting on the other friction pad decreases as compared with the force acting on the friction pad on the piston side. Particularly, when the friction pad on the piston side approaches or passes over the central plane, which is defined between the friction pads when the friction pads are new, the force of the pad spring will be transmitted solely to the friction pad on the piston side, and the pad spring will sometimes be inclined and separate from the pad spring on the other side.